Composite panels of an aircraft are traditionally assembled by seals. These seals are generally required at abrupt or perpendicular interfaces. The interface between the belly fairing and the wing is an example of these abrupt interfaces.
Seals conventionally installed on these interfaces suffer frequent problems of breakage and noise. The reason is that the extremities of these conventional seals (from panel to panel) bat during the flight.
FIG. 1 shows a conventional panel assembly, in which the extremities of the panels 12, 13 are visibly damaged.
Since the mentioned situation is unacceptable for an aircraft, some aircraft manufacturers have developed alternative solutions for assembling panels. One of these solutions includes providing glued seals between the panels to be assembled. Typically, one extreme of these seals is glued to the surface of one of the panels, and the other extreme is attached to the other panel.
FIG. 2a shows a cross-sectional view of a glued seal 14 provided for the assembly between two panels 15, 16. The figure shows a Y-seal 14 having one extreme attached to a first panel 15, and an opposite extreme glued to a second panel 16. The seal 14 is filled with glue 17.
Although glued seals are widely used, they also carry several drawbacks. One of the main drawbacks relates to maintainability. In the glued solution, maintenance workers need to graze the glue at the surface to uninstall the panel. This is a very hard task (that airlines shall do mandatorily for regular inspections) with high risk of damaging the structure.
FIG. 2b shows the panel 16 shown in FIG. 2a, in which the glued seal 14 has been removed. As shown, the panel 16 has glue 17 residues that have to be cleaned.
Further, glue is hard and difficult to apply. Also, it is not a reproducible solution (depending on the operator) and is very high time consuming.
In addition, glue involves a not negligible increase of weight, which can be around 14 kg.
Further, even applying the glued solution, there are some panels that still bat, generating noise and damage. To solve that, external plate parts are additionally installed, to stabilize the extremities of these problematic panels. These parts include aerodynamic (edges across to the airflow) and maintainability (needs to remove the part to uninstall one of the panels) penalties.
Regarding the installation of glued seals, it has to be noticed that panels have to be equipped with the seals, and installed one by one in the FAL (Final Assembly Line). The operator installs the panels first, and glues the seals to a panel surface. Afterwards he shall do an extra operation comprising or consisting of lifting the external lip of the seal and injecting the sealant (glue) to fill up the volume (see FIG. 2a) between lips of the seal. Once the volume is filled, sealant is getting out from the extremities and everything has to be cleaned.
Applying the glue is a long lasting task, considering the difficult access the operators have to the panel assemblies, since the application has to be done once everything is installed. Further, it is a manual and dirty operation, which shall be done not only one time in FAL to deliver the aircraft, but also in service by the airlines.
It would therefore be desirable to provide a technical approach that offers a solution for assembling panels that is capable of improving the performance, noise, maintenance and endurance of the conventional solutions.